From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=5.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED, RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by inbox.vuxu.org (Postfix) with SMTP id 4566A2D3D9 for ; Thu, 29 Aug 2024 21:11:54 +0200 (CEST) Received: (qmail 1576 invoked by uid 550); 29 Aug 2024 19:11:50 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 1531 invoked from network); 29 Aug 2024 19:11:50 -0000 Mime-Version: 1.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ayaya.dev; s=key1; t=1724958702; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=K9lzAzoWQKaoJuJZlyp6Sqyw3/wchva+k+Y4p80aGv8=; b=Kw6uRmUerA6zWY0nbkyG38iA9JB2GEFwTuRNPVm4xYUYWWk9x5lOYfKA6y844afVMAqzW9 940Zxeu4dCPx/HnhqnLO9bJhUjUeZ+nJqvUrI+pyVqjV5f5mvzMWx4qMyrBvVSNpkoSZjd 2/IY+Sns9ih/D5B1CedO//z6a7kCcaA= Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 29 Aug 2024 21:11:38 +0200 Message-Id: Cc: X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: "alice" To: "Rich Felker" References: <20240829125727.GK10433@brightrain.aerifal.cx> <20240829190348.GL10433@brightrain.aerifal.cx> In-Reply-To: <20240829190348.GL10433@brightrain.aerifal.cx> X-Migadu-Flow: FLOW_OUT Subject: Re: [musl] [PATCH] fix MINSIGSTKSZ and SIGSTKSZ for powerpc64 On Thu Aug 29, 2024 at 9:03 PM CEST, Rich Felker wrote: > On Thu, Aug 29, 2024 at 06:00:52PM +0200, alice wrote: > > On Thu Aug 29, 2024 at 2:57 PM CEST, Rich Felker wrote: > > > On Thu, Aug 29, 2024 at 05:38:42AM +0200, psykose wrote: > > > > since kernel commit 2f82ec19757f58549467db568c56e7dfff8af283 > > > > (https://github.com/torvalds/linux/commit/2f82ec19757f58549467db568= c56e7dfff8af283) > > > > the kernel has updated these minimum values. having these small val= ues breaks > > > > sysconf(_SC_MINSIGSTKSZ) too; it returns 4224 in musl currently whi= ch ends up > > > > returning ENOMEM from the syscall made in sigaltstack. > > > >=20 > > > > raising these to match the kernel fixes sigaltstack use on powerpc6= 4(le). > > > > caught by glib's 2.82 testsuite > > > > > > I don't follow how you're claiming sysconf(_SC_MINSIGSTKSZ) is broken= . > > > It will just return the kernel-provided value on new kernels that > > > insist on having a larger stack. In particular I don't see where the > > > value 4224 is supposed to be coming from. If there's something I'm > > > missing, please explain. > >=20 > > sysconf(_SC_MINSIGSTKSZ) returns 4224 on ppc64le (this is as far as i k= now > > expected). > > I don't have a real system handy to test on, so I'm executing this > mentally, and not seeing where 4224 comes from. > sysconf(_SC_MINSIGSTKSZ) should return the kernel-provided value from > __getauxval(AT_MINSIGSTKSZ) unless it's less than the fixed macro > value MINSIGSTKSZ. Since that's 4096, the only way I can see this > happening is if the kernel filled in AT_MINSIGSTKSZ as 4224, which > would be a kernel bug...? yes, that getauxval gives 4224. feel free to forward it to the right place if you think it's a kernel bug := ) (it might just be an oversight since it was coordinated with glibc and so n= o programs ever hit this as glibc made the minimum match the 8192 correctly..= ) > > setting stack.ss_size =3D 4224 (from that call) and passing it to sigal= tstack > > returns ENOMEM because it is smaller than 8192 which the kernel enforce= s. > >=20 > > ...so the normal way of using sigaltstack with the smallest size (with = sysconf or > > the macros) is broken. > > making the MINSIGSTKSZ match the actual value the kernel enforces fixes= it. > > What the kernel enforces varies by version and possibly also hardware > capabilities. evidently it's enforcing exactly what that commit says that minsigstksz is = (now) on ppc64*, since setting ss_size to 8191 gives ENOMEM and setting it to 819= 2 works. you can wait for a hypothetical fix to __getauxval(AT_MINSIGSTKSZ) to also return 8192 if you want, but programs that use the macro defined value will remain broken if it isn't changed and clearly that is the minimum value on = new kernels :) i'll keep the patch downstream in any case > > Rich